Hardwood Record — Veneer & Panel Section 



27 



Progress in Airplane Products 



Veneer and Panel Industries Should Be Able to Forge Ahead 



jp^^iC) DKTAIL of airplane construction has been at- 

 1^1 tended by the necessity for more careful study 

 HJ ^J|| or more revolutionary methods than have the 

 inakiiiK ol <^lued-up panels for fusilages and of lamina- 

 tions of solid lumber for propellers. The two lines of 

 work, of course, present entirely divergent problems. 



in the propeller lamination the principal object has been 

 to insure glue that would give strength equal to or greater 

 than that of the wood itself and to insure its standing 

 up under strenuous usage. On account of the thickness 

 of propeller laminations and the possibilities of approach- 

 ing or even possibly reaching waterproof quality in the 

 coating or the final finish of the propeller, waterproof 

 glue as a binder for the laminations has not been con- 

 sidered absolutely essential, though the trend is now 

 toward the use of such glues in propellers. On the other 

 hand, glue used in veneered panels forming fusilages 

 or bodies must be definitely waterproof as well as of a 

 high quality from the standpoint of adhesion. Work has 

 been carried on at three sources — by the manufacturers 

 of hide and waterproof glues, by the manufacturers of 

 panels, and by the Forest Products Laboratory at Madi- 

 son. Wis. The latter department acting for the govern- 

 ment carried on research work and the final tests. There 

 has been close and constant co-operation between the 

 various interests applying themselves to the problems. 



In propeller construction hide glue is used. Work on 

 this phase of the problem has been directed toward main- 

 taining a standard quality in hide glue production and 

 svorking out specifications that would adapt themselves 

 to practice. This problem has been solved with the fol- 

 lowing result: The Forest Products Laboratory, through 

 extensive tests, has determined the necessary specifica- 

 tions for glue to be used in propeller construction. It 

 has arrived at a final working basis for specifications 

 which have been adopted by the Signal Corps as official 

 and does not call for the acceptance of this or that make 

 of glue. The tests taken, except, of course, the final test 

 for acceptance or rejection of the finished a'rplane or 

 propeller, will be of the glue alone and not as a part of 

 the completed article. The Signal Corps' inspector takes 

 a sample from each barrel of glue ready for shipment 

 from the glue factory and then seals the barrel and for- 

 wards the sample to the laboratory. The tests are then 

 made of this particular sample as a representative of the 

 barrel from which it was taken. If the sample passes, the 

 barrel of which it was a part is approved for use in pro- 

 peller construction. If the sample does not pass, the 

 barrel is rejected for this use. As these tests are of a 

 specific and uniform nature and as glues from sufficient 

 sources of supply have already passed, it can be said that 

 this problem is solved. 



The work in developing waterproof glue has not been 

 so simple. The commercial panel of the domestic trade 

 has not been bound with waterproof glue, although for 

 years experiments looking toward development of water- 

 proof glues for commercialwork have been common. Most 

 of the products were outright failures and only recently — 

 in fact, only since the great need for waterproof panels 

 for airplanes has been manifest — has the waterproof glue 

 proposition appeared to reach anything like a tangible 

 position in this country. Russian processes have been suc- 

 cessful for years, but have been secret and otherwise 

 L-navailable. 



At the advent of airplane demand many new experi- 

 menters entered the field and work was speeded up on 

 waterproof glue processes which have been recognized 

 in commercial practice as at least partially successful. 

 The contact with the government has in all cases been 

 brought about through the Madison laboratory, which 

 has made tests of dozens of glues for which water-resist- 

 ant qualities were claimed and of panels submitted by 

 many firms which claimed waterproof properties for the 

 binders respectively used. While it appeared that the 

 development of waterproof panels was blocked by the 

 necessity for hot presses in their manufacture, this ap- 

 peared an obstacle because the facilities for manufactur- 

 ing hot plate presses were totally inadequate and could 

 not be rapidly expanded. New formulas, however, allow 

 of the manufacture of waterproof panels in cold presses 

 and thus production of acceptable panels can come from 

 either source. 



Leaving consideration of the raw glue, we come to the 

 question of its application. The glue using industry or 

 that pprtion of it interested in airplane work is confronted 

 with a better situation here than existed in commercial 

 practice before the war. First, it has an augmented supply 

 of higher quality hide glue and the authoritative help of 

 the laboratory to guarantee the quality of the shipments 

 it receives. Those interested in the panel end are assured 

 of a nearer approach to an adequate supply of water 

 resisting glue and the constant help of the government 

 through the laboratory to the end that such glue may be 

 constantly improved and its supply steadily enlarged. 

 The need comes then for correct practice in laying the 

 veneers so that the finished panels may come within 

 specifications of the Signal Corps. It seems that with the 

 glue situation rapidly approaching clarification, the biggest 

 obstacle now in the way of airplane panel production 

 is found at the point of contact between the panel makers 

 and the airplane factory. 



The chief difficulties are found in specifications for the 

 panels (and the veneers from which they are made) 

 and in the inspection for acceptance or rejection for 



